Small electronic components, such as integrated circuit chips or devices, terminal pads of printed circuit boards, liquid crystal displays, etc. typically have bonding locations for electrical interconnection to circuitry external to the particular device. In many instances, the spacings required between each electrical interconnection are extremely close, i.e., on the order of 0.1 mm for chips, and electrical isolation must be maintained between adjacent connections.
One technique for electrical bonding such components is through the utilization of an array of contact points spread over the face of the device (also known as "flip chip" devices). Such contact points in such devices are commonly electrically connected to external circuitry by aligning the array of bonding locations with corresponding bonding locations on the external circuitry and forming a metallurgical bond between the two sets of bonding locations by, for example, reflow soldering. In such instances, the arrays of bonding locations often comprise metallized bumps or protrusions extending above the surface of the device.
Such techniques typically have serious drawbacks. First, the coefficients of thermal expansion between the electronic components to be connected can vary greatly, which may cause physical stress on the metallurgical bond between the bonding locations during the thermal cycling encountered during testing and use of the assembled parts. Second, it is normally necessary to remove heat generated during electrical functioning of the device. One of the most effective means of such removal is by conducting the heat from the device to an adjacent substrate, which can best be accomplished by maximizing the contact between the semiconductor or electronic device and, for example, its ceramic package. In the case of flip chip devices, however, the contact area to the surrounding package is often limited to the area of the metallurgical bonds, which can comprise as small as five percent of the total area of the device, thus severely impairing removal of heat from the device to the adjacent substrate.
A second technique is based on the use of conductive particles to provide the necessary contact. Such particles are contained within a polymeric, typically adhesive, system such that the particle surfaces extend from one face of the adhesive to the other. When electrical connection is to be made, pressure is applied to the contact area to compress or deform the particles to maximize the electrical contact.
This technique suffers from a severe drawback when contact spacings are on a fine pitch. This is because such systems have random spacing between conductors. Voids or clusters of particles are common, thus leading to short circuiting with fine pitch spacings of contacts.
In contrast thereto,, the present system affords extremely uniform spacing of conductors for ease of use with fine pitch contact spacings without short circuiting. In addition, the extreme uniformity of the height and deformability of our conductive passages, and thus the reduced bonding forces necessary to provide stable contact areas is a distinct and heretofore unavailable advantage over these prior techniques.